The invention concerns an energy supply chain, more specifically for example an energy supply chain for guiding at least one conduit such as a cable, hose or the like between a stationary and a movable connection location or between first and second connection locations which are movable relative to each other.
It may be noted at this point that a typical area of use of such an energy supply chain is as a guide means for guiding conduits, hoses and/or cables for the external supply of application installations such as gripping arms, welding tongs, spray guns and the like on robot arms having a plurality of degrees of rotational and/or pivotal freedom.
The task of guiding conduits such as hoses and/or cables for carrying energy for example in the form of power, water, compressed air or hydraulic fluid for the external supply of application installations on robot arms has hitherto been implemented by corrugated flexible polyurethane tubes which are equipped in various different ways. In this respect the term application installation is used to denote for example gripper arms, welding tongs, spray guns or the like which are disposed at the distal ends of the robot arms. In regard to such installations, the supply hoses and cables or conduits are passed and fixed outside cavities which are formed within the robot arms themselves. As it is known that robot arms have a plurality of degrees of rotational and/or pivotal freedom, the guide means for the supply conduits, in other words the above-mentioned guide tubes or hoses, must also be capable of implementing a plurality of pivotal and torsional movements. The radii of curvature of the guide tubes or hoses must be such that changes in length between the application installation at the distal end of a robot arm and a connection point, for example at the base of the robot arm, can be compensated. The radii of the cable or hose guide means which is laid on the robot arm, in the form of the flexible polyurethane tube or hose, are so selected that they themselves form a reserve or buffer for accommodating variations in length in that way, and they thus form a length-compensating configuration between the connection point for example at the base of the robot arm and the application installation at the robot arm distal end. When however there is a very short distance between the application installation and the connection point, being a situation in which the maximum lengthwise portion of the guide tube has to be accommodated in the length-compensation buffer, the excessive radii of the guide tubes or hoses have a tendency to hang down. Such sagging of the guide tubes or hoses should be avoided as far as possible as that downwardly hanging configuration of the guide tube or hose can have an adverse effect on the freedom of movement of the robot arm.
In order to obviate this problem, the portions of the guide tube or hose which are operative to form radii therein can be arranged in coil springs or spring turns which afford to the radius in question a certain degree of rigidity which opposes such sagging of the guide tubes or hoses.
The guide tube or hose may also be held in guide sleeves which are fixed on spring supports. The spring supports also act in opposition to sagging of the guide tube or hose in the radius of curvature in question.
Both of the above-described configurations for stabilising the radii of the guide tubes or hoses however suffer from the disadvantage that, depending on the flexural and torsional loading on the guide tube or hose, the latter, in the stabilised region, deflects in a completely uncontrolled fashion in the direction of the lowest level of resistance to flexural or torsional forces. That gives rise to completely uncontrolled loadings in the guide tube or hose while some situations also involve resistances to movement, which hinder movement of the robot arm in the prescribed direction.
Finally, the use of guide tubes involves the disadvantage that they can exceed the maximum amount of bending or the maximum flexural loading, which is acceptable in regard to the supply conduits contained therein. Particularly in the case of uncontrolled deflection or bulging of the guide tubes or hoses in the region of the stabilised radii thereof, both the guide tubes or hoses and also the internal components therein may suffer from unacceptable kinking or folding loadings.
An object of the present invention is to provide an energy supply chain for guiding conduits such as cables, hoses or the like, of a simplified structure and capable of stabilising flexural radii, without suffering from the disadvantages referred to above of the prior arrangements.
Another object of the present invention is to provide an energy supply chain for cables, hoses or the like conduits of a simple and operationally reliable structure for serving as a guide means for the external supply of components on a robot arm having a plurality of degrees of rotational and/or pivotal freedom.
Still another object of the present invention is to provide an energy supply chain for guiding at least one conduit between first and second connection locations of which at least one is movable relative to the other, which is of a simplified and easily assemblable structure with a low level of susceptibility to faults while allowing smooth pivotal and sliding movement in operation thereof.
In accordance with the principles of the present invention the foregoing and other objects are attained by an energy guide chain for guiding at least one conduit such as a cable or hose between first and second connection locations of which at least one is movable relative to the other, for example a stationary and a movable connection location, for example to act as a guide means for guiding a hose and/or a cable for external supply to a component on a robot arm having a plurality of degrees of rotational and/or pivotal freedom, comprising a plurality of chain link members with means pivotably interconnecting the chain link members to form the elongate chain. The chain link members form a receiving space for the conduit to extend therein. The chain further includes at least one elongate bar which is resilient about its longitudinal axis and which extends in the longitudinal direction of the chain in the receiving space thereof and which upon pivotal movement of the chain link members relative to each other produces return forces opposing the pivotal movement.
In a preferred feature of the invention the bar of at least some chain link members is arranged displaceably in the longitudinal direction upon curvature of the energy supply chain so that any pivotal or curvature radii can be implemented in a simple manner without being adversely affected by the bar which forms a stabilisation element for the chain. With increasing flexing thereof, the bar generates return forces which seek to cause the energy supply chain to move into a straight condition.
In order to counteract uncontrolled deflection movements of the energy supply chain when pivotal movements thereof are effected, the energy supply chain preferably includes first and second bars, for example of glass fiber, which extend at least over a part of the length of the chain. In a preferred feature, those bars extend only in the region of the radii where a stabilisation effect is required, in which respect the portion of the chain which is to be stabilised can advantageously be suitably adjusted by altering the length of the bars. The use of first and second bars affords the advantage that the return forces generated thereby can be applied symmetrically to the chain, thereby also at least substantially obviating uncontrolled deflection movements of the chain. In quite general terms an energy supply chain which is comparatively stiff in comparison with a polyurethane tube or hose already resists uncontrolled deflection movement by virtue of spring forces which are applied thereto.
In a further preferred feature of the invention the bar or bars is or are each arranged in a respective guide tube or hose so that a sliding movement or a relative movement of the bars when a plurality thereof is present is possible upon flexing of the energy supply chain in respect of a part of the flexural radius thereof without frictional effects or edges in the interior of the chain having an adverse effect. Preferably, the at least one bar is fixed outside the energy supply chain or to an end fixing portion of the chain, at an end thereof, for example by means of a suitable clamping clip.
The guide tube or tubes desirably extend between the connection locations of the chain.
With that design configuration, the bar or bars can be easily interchanged and replaced by other bars of different thicknesses affording different return forces. The operative length of the spring configuration produced by the bars can be easily adjusted by withdrawing the bars. Finally the bars can also be replaced in that way without the energy supply chain or the conduits, cables or hoses or the like guided therein having to be disconnected at the connection locations.
In accordance with a particularly preferred feature of the energy supply chain according to the invention at least in a portion-wise manner a plurality of mutually adjacent chain link members have relative to each other first and second degrees of pivotal freedom, the pivot axes thereof preferably being oriented displaced through 90xc2x0 relative to each other, while the chain link members have at least in the region through which the at least one bar passes only one respective degree of pivotal freedom relative to each other, which is in the respective same direction, so that in this way also it is possible to at least substantially avoid unacceptable and uncontrolled deflection of the energy supply chain at the respective flexing radius in a direction which cannot be foreseen.
An energy supply chain of a similar configuration can be found for example in DE 43 02 757 C1 to which reference is directed here. Such an energy supply chain has in a portionwise manner two degrees of freedom, in respect of rotation of a plurality of mutually adjacent elements or chain link members, wherein each second element is arranged turned through 90xc2x0 about the longitudinal axis of the cable guide configuration formed in that way, so that three elements are connected together in a semi-cardanic manner and the energy supply chain has in a portion-wise fashion overall three degrees of pivotal or rotational freedom. Such an energy supply chain is particularly suitable for implementing the movements to be performed by a robot arm, in which respect advantageously the region of the radii to be stabilised for the energy supply chain obviously has only one degree of pivotal freedom of the chain link members relative to each other.
In a further preferred feature of the invention the chain link members are each in the form of an element with a closed external contour and a closed external surface so that they form a very substantially closed passage as the receiving space for the conduit. In accordance with a preferred feature the energy supply chain can be formed by chain link members of thermoplastic material.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of a preferred embodiment thereof.